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Screen and Form capture with Managed C++

, 3 Jul 2002
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This is further demonstration of MC++ IJW capabilities

Introduction

I was continuing to play around with IJW. And when I realized that there was no direct Screen Capture method in .NET, I thought I might as well try to make a simple Screen Capturing program. Of course since I knew as much about GDI programming as some of these Canadians seem to know about Cricket, you might as well have guessed that I found things more than a little difficult. Luckily Tom Archer, James Johnson and Neil Van Note promptly answered my questions.

The sample program allows you to capture the entire screen or only the current form and also allows you to save the image, though here I have hard coded the filename and path, as I was too lazy to show a save dialog. If you repeatedly click on the capture buttons, you get a weird effect of cascading screen captures, one on top of the other as shown in the screenshot of the sample program.

Quick Rundown

Using GetDC or GetWindowDC depending on whether we are capturing the screen or the current window, we get our HDC using which we call CreateCompatibleDC to create our memory DC. Using a call to GetSystemMetrics we get the size of the screen and then call CreateCompatibleBitmap to create a bitmap. Then we select this bitmap into the memory DC using a call to SelectObject and save the old bitmap. Using BitBlt we copy the screen or window contents into this bitmap which is now selected into the memory DC. Then we select the original bitmap back into the DC, delete the memory DC, release the DC, and delete the bitmap. To be frank, there is not much .NET stuff involved in the code, but imagine if you had to write all this using C#. Think of all the P/Invoke stuff you'd have to do and the ugly declarations you'd have had to write for the API calls. With MC++ you are saved all that bother.

Full Source Listing

The source code is self-explanatory. Notice how I have written my WinMain. This is because I am including windows.h where WinMain is already prototyped in that fashion.

#include "stdafx.h"

#using <mscorlib.dll>
#using <System.dll>
#using <System.Drawing.dll>
#using <System.Windows.Forms.dll>

#include <tchar.h>
#include <windows.h>

using namespace System;
using namespace System::ComponentModel;
using namespace System::Drawing;
using namespace System::Windows::Forms;

public __gc class NForm : public Form
{
public:
    Button *btn;
    Button *btn2;
    Button *btn3;
    PictureBox *pbox;
    void btn_Click(Object *sender, System::EventArgs* e); 
    void CaptureScreen(bool FullScreen);

    NForm()
    {
        this->StartPosition = FormStartPosition::CenterScreen;
        this->Text = "Capture screen - Nish for CodeProject -IJW";
        this->Size = Drawing::Size(750,550);
        this->FormBorderStyle = System::Windows::Forms::FormBorderStyle::FixedDialog; 

        btn=new Button();
        btn->Text="Capture Screen";
        btn->Location=Point(5,5);
        btn->Size=Drawing::Size(100,30);
        btn->add_Click(new EventHandler(this,&NForm::btn_Click)); 
        this->Controls->Add(btn);

        btn2=new Button();
        btn2->Text="Capture Form";
        btn2->Location=Point(125,5);
        btn2->Size=Drawing::Size(100,30);
        btn2->add_Click(new EventHandler(this,&NForm::btn_Click)); 
        this->Controls->Add(btn2);

        btn3=new Button();
        btn3->Text="Save C:\\Z.Jpg";
        btn3->Location=Point(250,5);
        btn3->Size=Drawing::Size(100,30);
        btn3->add_Click(new EventHandler(this,&NForm::btn_Click)); 
        this->Controls->Add(btn3);

        pbox = new PictureBox();
        pbox->Location=Point(5,45);
        pbox->Size=Drawing::Size(730,470);
        pbox->BorderStyle = BorderStyle::Fixed3D;
        pbox->SizeMode = PictureBoxSizeMode::StretchImage;


        this->Controls->Add(pbox);
    }
};

int __stdcall WinMain(HINSTANCE,HINSTANCE,LPSTR,int)
{
    Application::Run(new NForm());
    return 0;
}

void NForm::btn_Click(Object *sender, System::EventArgs *e)
{
    if(sender->Equals(btn))
        CaptureScreen(true);
    else
    {
        if(sender->Equals(btn2))
            CaptureScreen(false);
        else
            pbox->Image->Save("C:\\Z.Jpg",
                Drawing::Imaging::ImageFormat::Jpeg);
    }
}

void NForm::CaptureScreen(bool FullScreen)
{
    HDC hDC;
    if(FullScreen)
        hDC = GetDC(NULL); //Get full screen
    else
    {
        HWND hWnd=(HWND)this->Handle.ToInt32(); //Get HWND of form
        hDC = GetWindowDC(hWnd); //Now get it's DC handle 
    }
    HDC hMemDC = CreateCompatibleDC(hDC);
    RECT r;
    GetWindowRect((HWND)this->Handle.ToInt32(),&r); //need this for Form
    SIZE size;
    if(FullScreen)
    { 
        size.cx = GetSystemMetrics(SM_CXSCREEN);
        size.cy = GetSystemMetrics(SM_CYSCREEN);
    } 
    else
    {
        size.cx = r.right-r.left;
        size.cy = r.bottom-r.top;
    }

    //most of the remaining code is normal GDI stuff

    HBITMAP hBitmap = CreateCompatibleBitmap(hDC, size.cx, size.cy);
    if (hBitmap)
    {
        HBITMAP hOld = (HBITMAP) SelectObject(hMemDC, hBitmap);
        BitBlt(hMemDC, 0, 0, size.cx, size.cy, hDC, 0, 0, SRCCOPY);
        SelectObject(hMemDC, hOld);
        DeleteDC(hMemDC);
        ReleaseDC(NULL, hDC);
        pbox->Image = Image::FromHbitmap(hBitmap); 
        DeleteObject(hBitmap);
    }
}

History

  • May 7 02 - Posted the article
  • Jul 4 02 - Added sample VC++ project

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

About the Author

Nish Sivakumar

United States United States
Nish is a real nice guy who has been writing code since 1990 when he first got his hands on an 8088 with 640 KB RAM. Originally from sunny Trivandrum in India, he has been living in various places over the past few years and often thinks it’s time he settled down somewhere.
 
Nish has been a Microsoft Visual C++ MVP since October, 2002 - awfully nice of Microsoft, he thinks. He maintains an MVP tips and tricks web site - www.voidnish.com where you can find a consolidated list of his articles, writings and ideas on VC++, MFC, .NET and C++/CLI. Oh, and you might want to check out his blog on C++/CLI, MFC, .NET and a lot of other stuff - blog.voidnish.com.
 
Nish loves reading Science Fiction, P G Wodehouse and Agatha Christie, and also fancies himself to be a decent writer of sorts. He has authored a romantic comedy Summer Love and Some more Cricket as well as a programming book – Extending MFC applications with the .NET Framework.
 
Nish's latest book C++/CLI in Action published by Manning Publications is now available for purchase. You can read more about the book on his blog.
 
Despite his wife's attempts to get him into cooking, his best effort so far has been a badly done omelette. Some day, he hopes to be a good cook, and to cook a tasty dinner for his wife.

Comments and Discussions

 
GeneralMy vote of 5 PinmemberAziz Yosofi6-Feb-13 22:25 
Questionexcuse me, i have a problem in capturing when i play the video Pinmemberzhmx_love21-Aug-12 22:47 
GeneralMy vote of 5 PinmemberMember 923867912-Jul-12 22:27 
QuestionQuestions regarding your article PinmemberOlariu Bogdan25-May-10 1:23 
AnswerRe: Questions regarding your article PinmvpNishant Sivakumar25-May-10 1:29 
GeneralRe: Questions regarding your article PinmemberOlariu Bogdan25-May-10 23:39 
Questionhow to get the image containing total content of entire form in .net windows application Pinmemberm.raghu18-Jun-07 19:13 
QuestionHow CreateDIBSection Work??? Pinmemberjavad_200524-Sep-06 9:32 
QuestionC++/CLI Image::FromHBitmap PinmemberCoder2k25-Jun-06 8:35 
QuestionRe: C++/CLI Image::FromHBitmap PinmemberCoder2k25-Jun-06 10:01 
AnswerRe: C++/CLI Image::FromHBitmap PinmemberCoder2k25-Jun-06 10:15 
Generalproblem Pinmembermr_ander5on6-Jun-05 10:58 
Questionhow SetDIBitsToDevice work??? Pinmemberjags_vc17-Mar-05 18:23 
GeneralBlack Screen Pinmembersomeone3214824-Apr-04 14:10 
AnswerRe: Black Screen [modified] Pinmemberdamn_tiby27-Apr-07 6:39 
Generala question Pinsussyediyildiz1-Aug-02 23:02 
GeneralRe: a question PineditorNishant S1-Aug-02 23:11 
GeneralRe: a question Pinsussyediyildiz2-Aug-02 1:24 
Generaldoh Pinmemberem4-Jul-02 15:07 
GeneralGood work but.. PinmemberRama Krishna8-May-02 4:09 
GeneralRe: Good work but.. PinmemberNish [BusterBoy]8-May-02 8:56 
GeneralRe: Good work but.. PinmemberRama Krishna8-May-02 8:57 
GeneralRe: Good work but.. PinmemberNish [BusterBoy]8-May-02 9:08 
GeneralRe: Good work but.. PinsubeditorJames T. Johnson8-May-02 9:38 
GeneralRe: Good work but.. PinmemberNish [BusterBoy]8-May-02 9:42 

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